CINCINNATI — Comair Inc. has a new president only weeks after the failure of an overloaded computer system stranded hundreds of the Delta subsidiary's customers on Christmas.

Fred Buttrell, who had been serving as the head of Delta Air Lines Inc.'s Delta Connection group, immediately took over the presidency after Randy Rademacher's resignation after five years at the helm.

An internal Delta memo said Rademacher had stepped down to pursue other unspecified opportunities. Asked whether Rademacher was pressured to leave, Comair spokesman Nick Miller said: "It was his personal decision. We don't want to speculate on his reasons."

Miller said Tuesday that Rademacher would not be available through the company for comment. Rademacher's home phone number is not listed.

At least one analyst blamed Rademacher's departure on the Christmas fiasco that resulted in the cancellation of approximately 1,100 flights. It took Comair until Dec. 29 to return to operating a full daily flight schedule. The company blamed numerous passenger scheduling changes because of an ice storm for overloading the computer system.

"It's pretty obvious what happened over the holiday was very serious," said Doug Abbey, a partner of The Velocity Group, an aviation consulting firm based in Washington, D.C. "That's what this is all about."

Comair, which operates in 119 cities, carries about 30,000 passengers daily in the United States, mostly east of the Mississippi River, and to Canada and the Bahamas.

Its Christmas meltdown came during the same weekend that financially plagued US Airways Group experienced a similar fiasco because of labor issues and bad weather.

But unlike US Airways and even Comair parent Delta, which has come close to filing for bankruptcy, Comair's balance sheet has received little attention.

Delta doesn't reveal how much profit Comair brings to the Delta system. But former Delta chief executive Leo Mullin said several years ago that collective revenue from Comair and other Delta Connection carriers that coordinate schedules with Delta was in the billions of dollars annually.

Rademacher joined Comair in 1985. His presidential tenure included guiding the airline through a three-month strike by its pilots that won them pay increases in a new contract.

In a letter Monday, Buttrell, 42, told Comair's 6,000 employees that Comair must focus on improving the safety and reliability of its operations and customer service, along with a strategic plan to build its strength as a regional carrier.

"We will need every bit of your spirit and passion to take on the hard work necessary to put Comair back in the leadership position that built the company over the years," Buttrell wrote.